CF381B.Sereja and Stairs

普及/提高-

通过率：0%

AC君温馨提醒

该题目为【codeforces】题库的题目，您提交的代码将被提交至codeforces进行远程评测，并由ACGO抓取测评结果后进行展示。由于远程测评的测评机由其他平台提供，我们无法保证该服务的稳定性，若提交后无反应，请等待一段时间后再进行重试。

题目描述

Sereja loves integer sequences very much. He especially likes stairs.

Sequence $a_{1},a_{2},...,a_{|a|}$ ( $|a|$ is the length of the sequence) is stairs if there is such index $i$ $(1<=i<=|a|)$ , that the following condition is met:

a_{1}<a_{2}<...<a_{i-1}<a_{i}>a_{i+1}>...>a_{|a|-1}>a_{|a|}. For example, sequences [1, 2, 3, 2] and [4, 2] are stairs and sequence [3, 1, 2] isn't.

Sereja has $m$ cards with numbers. He wants to put some cards on the table in a row to get a stair sequence. What maximum number of cards can he put on the table?

输入格式

The first line contains integer $m$ $(1<=m<=10^{5})$ — the number of Sereja's cards. The second line contains $m$ integers $b_{i}$ $(1<=b_{i}<=5000)$ — the numbers on the Sereja's cards.

输出格式

In the first line print the number of cards you can put on the table. In the second line print the resulting stairs.

输入输出样例

输入#1
```
5
1 2 3 4 5
```
输出#1
```
5
5 4 3 2 1
```
输入#2
```
6
1 1 2 2 3 3
```
输出#2
```
5
1 2 3 2 1
```

首页